Metrohm 709 IC Pump - Manual (Page 29)

3.4 Pressure limit values for safety shutdown
709 IC Pump
21
3.4 Pressure limit values for safety shutdown
3.4.1 Minimum pressure limit
The minimum shutoff pressure of the pump can be set in steps of
0.1 MPa from 0.1 … 50 MPa with the pump drive switched on or off. Pro-
ceed as follows:
1 Select "P
min
"
Press <SELECT> key 4 until the "P
min
" LED 11 lights up.
2 Set shutoff pressure
Press < ↓ > key 5 or < ↑ > key 6 until the desired minimum
shutoff pressure (in MPa) appears in display 1.
3 Store shutoff pressure
Release < ↓ > key 5 or < ↑ > key 6: the value shown in display
1 at the time of release will be stored.
Entry of the value "0.0" switches off the lower pressure limit monitoring.
The set limit value should lie far enough below the particular operating
pressure. If the pump pressure falls below this preset lower limit during
operation, the microprocessor checks whether this violation persists for
several revolutions of the cam or whether it was a temporary drop in
pressure due to an air bubble or a brief leak in the valves. If the cause is
a temporary loss of pressure, the pump is not switched off. In the case
of a pressure drop due to leaks or interrupted inflow of the eluent, the
pump drive is switched off and disabled.
If the pump has been shut off by the minimum pressure monitoring, the
LED 11 flashes, the shutoff pressure can be requested in the display
"P
actual
" (see section 3.7). The safety shutdown is not active during the
first two minutes after the pump drive has been switched on with the
<R/S> key 3.
Pressing the <R/S> key 3 re-enables the pump drive, the LED 11 no
longer flashes and the pump is in the standby mode. Pressing the
<R/S> key 3 again puts the pump back into operation.